In this photo taken with a mobile phone, Tuesday, May. 7, 2013, Bakura Ibrahim, a suspected member of Islamic extremist group arrested by soldiers is tied to a tree in Bama, Nigeria. Coordinated attacks by Islamic extremists armed with heavy machine guns killed at least 42 people in northeast Nigeria, authorities said Tuesday, the latest in a string of increasingly bloody attacks threatening peace in Africa's most populous nation. The attack struck multiple locations in the hard-hit town of Bama in Nigeria's Borno state, where shootings and bombings have continued unstopped since an insurgency began there in 2010. Fighters raided a federal prison during their assault as well, freeing 105 inmates in another mass prison break to hit the country, officials said. (AP Photo/Abdukareem Haruna)

LAGOS, Nigeria (AP) — Admitting Islamic extremists now control some of his nation’s villages and towns, Nigeria’s president declared a state of emergency Tuesday across the country’s troubled northeast, promising to send more troops to fight what he said is now an open rebellion.

President Goodluck Jonathan, speaking live on state radio and television networks, also warned that any building suspected to house Islamic extremists would be taken over in what he described as the “war” now facing Africa’s most populous nation. However, it’s unclear what the emergency powers will do to halt the violence, as a similar past effort failed to stop the bloodshed.

“It would appear that there is a systematic effort by insurgents and terrorists to destabilize the Nigerian state and test our collective resolve,” Jonathan said.

Jonathan said the order will be in force in Adamawa, Borno and Yobe states. He said the states would receive more troops, though he will not remove state politicians from their posts. Under Nigerian law, the president has the power to remove politicians from their posts and install a caretaker government in emergency circumstances.

The president’s speech offered the starkest vision of the ongoing violence, often downplayed by security forces and government officials due to political considerations. Jonathan described the attacks as a “rebellion,” at one point describing how fighters had destroyed government buildings and “had taken women and children as hostages.”

“Already, some northern parts of Borno state have been taken over by groups whose allegiance are to different flags than Nigeria’s,” Jonathan said.

The president later added: “These actions amount to a declaration of war and a deliberate attempt to undermine the authority of the Nigerian state and threaten (its) territorial integrity. As a responsible government, we will not tolerate this.”

Since 2010, more than 1,600 people have been killed in attacks by Islamic insurgents, according to an Associated Press count. Recently, Nigeria’s military has said Islamic fighters now use anti-aircraft guns mounted on trucks to fight the nation’s soldiers, likely outgunning the country’s already overstretched security forces.

Meanwhile, violence pitting different ethnic groups against each other continues, with clashes that kill dozens at a time. In addition, dozens of police officers and agents of the country’s domestic spy agency were recently slaughtered by a militia.

One of the main Islamic extremist groups fighting Nigeria’s weak central government is Boko Haram, whose name means “Western education is sacrilege” in the Hausa language of Nigeria’s north.

The group has said it wants its imprisoned members freed and strict Islamic law adopted across the multiethnic nation of more than 160 million people. It has produced several splinter groups, and analysts say its members have contact with two other al-Qaida-linked groups in Africa.

The Islamic insurgency in Nigeria grew out of a 2009 riot led by Boko Haram members in Maiduguri that ended in a military and police crackdown that killed some 700 people.

The group’s leader died in police custody, in an apparent killing. From 2010 on, Islamic extremists have engaged in hit-and-run shootings and suicide bombings. Recently, however, they’ve begun to use military-grade weapons, some of which they apparently seized from Nigerian military stockpiles.

It remains unclear how much effect Jonathan’s announcement will have. In late December 2011, Jonathan declared a similar state of emergency over parts of four states, including Borno and Yobe. The extremist attacks continued despite that.

Nigeria’s military and police also have been repeatedly accused by human rights activists and others of torturing and summarily killing suspects, as well as burning down civilian homes and killing civilians in retaliation for militant attacks.

The latest incident, in a fishing village in Borno state along the shores of Lake Chad, saw at least 187 people killed and there are allegations that soldiers are responsible. While the military has denied repeatedly that it attacks and kills civilians, the country’s armed forces have a history of committing such assaults.

Separately on Tuesday, an official in the central Nigerian state of Kaduna said gunmen armed with assault rifles and suspected to be Hausa-Fulani cattle herders killed 11 people in a village there. And in Benue state, a government spokesman said an attack blamed on Hausa-Fulani cattle herders there killed at least 12 people.